1. Field of the Invention
The present invention relates to a resistive film touch panel, and particularly to a technique for detecting a simultaneous touch state (multi-touch state) in which the user touches multiple points.
2. Description of the Related Art
In recent years, it has become mainstream for electronic devices such as computers, cellular phone terminals, PDAs (Personal Digital Assistants), etc., to include an input apparatus which allows the user to operate the electronic device by using the fingers to touch the input device. Known examples of such input devices include resistive film touch panels (touch sensors) (Patent document 1).
In recent years, there is a demand for a touch panel which supports multi-touch operations. However, such touch panels have been realized only as electrostatic sensor touch panels, and have not been realized as resistive film touch panels. This is because, with such a resistive film touch panel, a position (coordinate) touched by the user is determined based upon the voltage output from the panel. However, such an arrangement is not capable of distinguishing between the output voltage of the panel in a case in which the user touches two positions (multi-touch operation) and the output voltage thereof in a case in which the user touches a single position (single touch operation).
Patent document 1 discloses a touch panel input apparatus which allows the user to perform multi-touch operations. However, this touch panel input apparatus handles such multi-touch operations as an input error. That is to say, such an arrangement does not actively support multi-touch operations as valid input operations. Thus, no technique has been disclosed which identifies the multiple coordinates involved in such a multi-touch operation.
The present applicant has created a technique for detecting the coordinates of multiple points touched at the same time on a resistive film touch panel (Japanese Patent Application No. 2009-48233). With such a technique, the current that flows through the panel is measured, and by considering the measurement result, the coordinates of such multiple points can be estimated.